As a test do the following. It may not solve the issue but the result will help me diagnose more
Access your website through what ever mechanism you can. find teh .htaccess file and take a backup of it ( This is critical )
then edit your file and replace everything with the solution 1 lines. if that dont work, try replacing all with solution 2 lines
Regards, MICK
Solution 1
RewriteEngine On
RewriteBase /
#uploaded files
RewriteRule ^(.*/)?files/$ index.php [L]
RewriteCond %{REQUEST_URI} !.*wp-content/plugins.*
RewriteRule ^(.*/)?files/(.*) wp-content/blogs.php?file=$2 [L]
# add a trailing slash to /wp-admin
RewriteCond %{REQUEST_URI} ^.*/wp-admin$
RewriteRule ^(.+)$ $1/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule . – [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-.*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*.php)$ $2 [L]
RewriteRule . index.php [L]
<IfModule mod_security.c>
<Files async-upload.php>
SecFilterEngine Off
SecFilterScanPOST Off
</Files>
</IfModule>
AddHandler phpini-cgi .php .htm
Action phpini-cgi /cgi-bin/php5-custom-ini.cgi
Solution 2
AddHandler phpini-cgi .php .htm
Action phpini-cgi /cgi-bin/php5-custom-ini.cgi
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ – [L]
RewriteRule . index.php [L]
